ATLANTA -- For years, Alan Carter worried what would happen to his wife, Mary, if a car wreck left them both unconscious.

Emergency medical personnel would have no idea she suffers from a brain injury --- the result of a 1989 head-on car crash that left her in a coma for 40 days, partially paralyzed, and unable to see out of one eye.

The sooner people with past brain injuries can receive the right treatment, Carter said, "the better chance they'll have overall."

Now, people such as his wife can voluntarily opt to list medical conditions on the back of their Georgia driver's license or state identification card by filling out an application and getting verification from a doctor.

The Georgia Department of Driver Services currently has 16 conditions --- including pacemaker, autism, hearing loss, seizures and diabetes --- from which drivers may choose. Others could be added in the future, agency spokeswoman Susan Sports said.

Advocates say having the option could aid emergency responders in knowing how to best treat people who may be unconscious. It also can help law enforcement officers who pull someone over determine whether a medical condition, such as a brain injury, may be a factor, said Carter, who leads a brain injury support group in Valdosta.

The designation may be especially helpful for people with hearing loss who are unable to hear instructions or someone with Tourette syndrome, a neurological disorder that can cause people to involuntarily blurt things out, said Mark Johnson, director of advocacy at the Shepherd Center, a rehabilitation hospital specializing in spinal cord and brain injuries.

"People make assumptions when people don't walk like everybody else or talk like everybody else or have a tic," Johnson said.

The department's decision to add the medical condition designations was spurred by a state Senate bill signed into law last year that allows people with post-traumatic stress disorder to put a notation on their licenses.

Sen. Ronald Ramsey, D-Decatur, said he got the idea from a veteran with PTSD who became anxious when he heard sirens or other loud noises. When a law enforcement officer pulled the veteran over, he felt the man was guilty of something, Ramsey said.

Veterans without any visible signs of injury should have some protection, he said. While privacy concerns were raised by some veterans groups, getting the notation is completely voluntary, Ramsey added.

"It could make the difference in saving a life," he said.

Added earlier this year, brain injury was the most recent medical condition to be included as an option. An estimated 1.7 million Americans suffer traumatic brain injuries each year, according to the Centers for Disease Control and Prevention.

Carter, 50, said he has spoken to state trooper cadets about the signs someone may have a brain injury instead of being under the influence of alcohol or drugs. They often don't have the outward appearance of someone who's been drinking, such as the smell of alcohol or a red complexion, Carter said. However, they may lean on the car for balance or hesitate to look a person in the eye, he said.

"Some of them have a tendency to get confused," Carter said. "They become nervous because of the challenge of answering questions."

A notation on the driver's license may help take away some of the guesswork, he said.

The brain injury Mary Carter suffered forced her to relearn how to get dressed and how to eat. It takes her longer to process information, and she tends to speak more slowly.

The 43-year-old, who doesn't drive but got the condition added to her license last month, said she thinks the option is a good idea. She has lost two medical alert bracelets in the past.

"If I was incapacitated, I could not tell them what was wrong," she said. "Who knows what would happen."